As is known, the piano generates sound when a key is depressed to cause a hammer to strike a string. Before the hammer comes in touch with the string, a damper is removed from the string. When key depression is stopped and the key is released, the damper again comes into contact with the string to check the string vibration and stop the sound.
As described above, sound generation and sound stop are carried out respectively by different mechanisms. Moreover, the keyboard, the hammer and the damper are connected to one another through many link mechanisms. For these reasons, the motion of the key and those of the hammer and damper differ with various play techniques such as staccato, legato, continuous key-striking and the like, so that it is impractical to relate them unitarily with one another. To reproduce the original play with fidelity using an automatic piano player apparatus, therefore, it is necessary to extract and record information of both the string-striking intensity of the hammer and that of the sound stop resulting from the key release on the keyboard.
In a conventional autopiano or automatic piano player apparatus, the key-depression information (sound stop information) is obtained from the keyboard portion and the string-striking intensity information of the hammer from the hammer or a catcher.
In the conventional apparatus described above, a sensor for obtaining the key-depression information (sound stop information) and a sensor for obtaining the string-striking intensity information of the hammer must be located at different positions. This gives rise to the problems of complicated adjustment procedures and a higher production cost.
The present invention has for its object to solve these problems observed with the prior art.
To accomplish the object described above, a sensor arrangement for an automatic piano player apparatus in accordance with the present invention comprises switches disposed in the proximity of a hammer system of a piano. The switches are turned on and off at a point of time A when a damper starts leaving a string in accordance with the rotating action of the hammer system. They are also activated at a point of time B when the hammer system has rotated through a predetermined angle, at a point of time C when the hammer system has rotated through a further predetermined angle and at a point of time D when the sound stops, respectively. The sensor arrangement also includes information output means for obtaining a key position information corresponding to a depressed key from the outputs of the switches, a string-striking intensity information corresponding to the time length between the point of time B and the point of time C from the outputs of the switches at the points of time B and C, and a state-of-condition information of the damper from the time between the point of time A and the point of time D from the outputs of the switches at the points of time A and D. The switches described above either comprise a first switch turning on and off at the points of time A, C and D and a second switch turning on and off at the point of time B, or comprise a first switch turning on and off at the points of time A and D, a second switch turning on and off at the point of time B, and a third switch turning on and off at the point of time C.
The first and second switches or the first, second and third switches are preferably disposed at desired distances apart in the rotating direction of the hammer system or at desired intervals in the radial direction with respect to the rotating plane of the hammer system. Preferably, each switch comprises a light emission element, a light reception element disposed opposite the light emission element and a shutter passing between the light emission element and the light reception element.